The long-term objective of this application is to evaluate whether menadione is a prototype compound for the development of a class of anticancer agents with a broad spectrum of action. Menadione inhibits the growth of tumor cells in culture including those exhibiting multiple drug resistance. The cytotoxicity of menadione is reversed by glutathione (GSH). It has also been shown that menadione depleted cellular GSH and damages DNA. The mechanisms responsible for menadione- mediated cytotoxicity and depletion of GSH are not known. In view of the broad spectrum of menadione and its potential in cancer chemotherapy, it is proposed to study: 1) the mechanism of depletion of GSH by examining the action of menadione on GSH-metabolizing enzymes, 2) the mechanism of cytotoxicity with emphasis on the cause and nature of menadione-induced DNA damage in relation to the depletion of GSH, 3) the interaction of menadione with other anticancer drugs where GSH plays a regulatory role; this will include examination of the relationship of cytotoxicity, DNA damage and GSH and 4) the biochemical determinants of menadione resistance and examination of the cross resistance of menadione with other clinically utilized anticancer agents. The techniques to be used to accomplish these specific aims will include alkaline and neutral elution, GSH pool measurements and enzyme assays, Southern and Northern blotting and clonogenic assays.